Answer:
4.125 inches.
Step-by-step explanation:
Based on the information provided we see that she took 90 minutes before shovelling which is 1 hour and 30 minutes or 1 1/2 hours (1.5 hours). Since we also know that the snow has been accumulating at a rate of 3/4 (0.75) inch per hour then we simply multiply these two values together to find out how much snow has accumulated.
0.75 * 1.5 = 1.125 inches
Now we can add this amount to the initial amount at 6:00 in the morning to find how many inches of snow were on the driveway when she started shovelling
3 + 1.125 = 4.125 inches.